In Texas Hold'em, this term refers to when a player receives the two cards needed to complete their hand on the turn (fourth street) and the river (fifth street). This is usually a hand they were not trying to make or a hand that is very unlikely based on the odds of hitting each card. This term is most commonly applied to hands such as the "backdoor flush" and "backdoor straight".
SoundPoker Says: A player who makes a "backdoor" hand usually holds hole cards of the same suit, or numerical connectors. For example if you held Q-J (spades) and the flop came 8 (hearts) - 2 (spades) - 4 (spades), the turn 10 (hearts) and the river 9 (clubs) this would be a straight Q-J-10-9-8. Since the two cards completed your hand on the turn and the river it would be considered a backdoor straight. Although you missed your flush draw you now have the straight nuts! If a spade would have came on board you would have to be weary of an opponent holding a higher kicker with either the Ace or King of spades.
See Also: Backdoor Flush, Backdoor Straight, Catching a card, Chase, Fish, Flush, Kicker, Runner-Runner, Straight
